1. Field
The field relates to a pixel and an organic light emitting display device using the same, and more particularly, to a pixel capable of compensating for deterioration of an organic light emitting diode and an organic light emitting display device using the pixel.
2. Description of the Related Technology
There are various types of flat panel display devices having reduced weight and volume when compared to cathode ray tubes. The flat panel display devices include liquid crystal display devices, field emission display devices, plasma display panels, organic light emitting display devices, and the like.
An organic light emitting display device displays images using organic light emitting diodes that emit light through recombination of electrons and holes. The organic light emitting display device has a fast response and is driven with low power consumption.
FIG. 1 is a circuit diagram of a pixel of a conventional organic light emitting display device.
Referring to FIG. 1, the pixel 4 of the conventional organic light emitting display device includes an organic light emitting diode OLED and a pixel circuit 2 connected to a data line Dm and a scan line Sn to control the organic light emitting diode OLED.
An anode electrode of the organic light emitting diode OLED is coupled to the pixel circuit 2, and a cathode electrode of the organic light emitting diode OLED is coupled to a second power source ELVSS. The organic light emitting diode OLED emits light having luminance corresponding to current supplied from the pixel circuit 2.
When a scan signal is supplied to the pixel circuit 2 through the scan line Sn, the pixel circuit 2 controls an amount of current supplied to the organic light emitting diode OLED in response to a data signal supplied through the data line Dm. For this purpose, the pixel circuit 2 includes a second transistor M2 coupled between a first power source ELVDD and the organic light emitting diode OLED, a first transistor M1 coupled to the second transistor M2, the data line Dm, and the scan line Sn, and a storage capacitor Cst coupled between a gate electrode and a second electrode of the second transistor M2.
A gate electrode of the first transistor M1 is coupled to the scan line Sn, and a first electrode of the first transistor M1 is coupled to the data line Dm. A second electrode of the first transistor M1 is coupled to one terminal of the storage capacitor Cst. Here, the first electrode is either of a source and a drain electrode, and the second electrode is the other. For example, if the first electrode is a source electrode, the second electrode is a drain electrode. When a scan signal is supplied to the first transistor M1 from the scan line Sn, the first transistor M1 is turned on so that a data signal supplied from the data line Dm is supplied to the storage capacitor Cst. As a result, the storage capacitor Cst stores a voltage corresponding to the data signal.
The gate electrode of the second transistor M2 is coupled to the terminal of the storage capacitor Cst, and a first electrode of the second transistor M2 is coupled to the other terminal of the storage capacitor Cst and the first power source ELVDD. The second electrode of the second transistor M2 is coupled to the anode electrode of the organic light emitting diode OLED. The second transistor M2 controls an amount of current flowing from the first power source ELVDD to the second power source ELVSS via the organic light emitting diode OLED, corresponding to the voltage stored in the storage capacitor Cst. As a result, the organic light emitting diode OLED emits light corresponding to an amount of current supplied from the second transistor M2.
However, in the conventional organic light emitting display device, an image having a desired luminance cannot be displayed due to efficiency variation caused by deterioration of the organic light emitting diode OLED. In other words, the organic light emitting diode deteriorates with time, and accordingly, an image having a desired luminance cannot be displayed. As an organic light emitting diode deteriorates, light having low luminance is emitted from the organic light emitting diode.